So now what happens? Our prime minister is up to his neck in it. His attorney general appears to have changed his advice about the legality of the war a few days before it began. Blair refuses to release either version, apparently for fear that he will be exposed as a liar and a war criminal. His government seems to have been complicit in the illegal bugging of friendly foreign powers and the United Nations. It went to war on the grounds of a threat which was both imaginary and known to be imaginary. Now the opposition has withdrawn from his fake inquiry. Seldom has a prime minister been so exposed and remained in office. Surely Blair will fall?

Not by himself, he won't. If we have learned anything about him over the past few months, it's that he would rather stroll naked round Parliament Square than resign before he has to. The press has a short attention span, Iraq is a long way away and the opposition is listless and unpopular. He has everything to gain by sweating it out.

In many ways, the strength of the case against the prime minister has been an advantage to him: our tendency is to assume that he is so badly wounded that all we need to do is to sit back and watch him bleed to death. But we reckon without the clots who run the country.

British people know that our legal system stinks. Over the past week, the attorney general's conflicts of interest have been exposed three times. First we discover he instructed that a prosecution be dropped when the case threatened to reveal his own advice to the prime minister. Then we discover that he took his decision in consultation with the government. The "Shawcross principle" he invoked in the House of Lords (ministers shall be consulted over a decision to prosecute) sounds very grand. What it means, of course, is that the law is applied only when it is politically convenient. Thirdly we find that he changed his professional opinion about the legality of the war to suit Blair's political needs.

We also know that our MPs are weak and frightened, that the civil service remains in the grip of the upper middle classes and that the press is run by multimillionaires, whose single purpose is to make this a better world for multimillionaires. Yet somehow we continue to trust that all these twisted instruments will deliver us from evil, that the sound chaps in the system will ultimately do the decent thing. How we reconcile our understanding with our belief is a mystery, but this mystery is a perennial feature of British political life. As a result, we now wait for the establishment to bring Blair down. We could be waiting forever.

In other words, nothing happens now unless we get off our butts and make it happen. This means abandoning that very British habit of expecting someone else to act on our behalf. Worse still, it means recognising that, for all the complexities and evasions of a modern political system, the motive force of politics is still the people, and the people remain responsible for what is done in their name.

The formula for making things happen is simple and has never changed. If you wish to alter a policy or depose a prime minister between elections, you must take to the streets. Without the poll tax riots, Mrs Thatcher might have contested the 1992 election. If GM crops hadn't been ripped up, they would be in commercial cultivation in Britain today. In the 1990s, protesters forced the government to cut its road-building budget by 80%. Most of the cities where roads were occupied by Reclaim the Streets have introduced major traffic-calming or traffic-reduction schemes. Gordon Brown stopped increasing fuel tax in response to the truckers' blockades.

Direct action, in other words, works. Not always, of course: our submarines still carry nuclear missiles, our airports are still expanding, the 1994 criminal justice bill became law. But it works more consistently than anything else we do. It does not work in isolation - it must be accompanied by polite campaigns of lobbying and letter-writing - but it works because it ensures that the issue stays in the public eye, and therefore exposes the government to continued questioning.

At length, if the campaign is well-organised and popular, the issue becomes a liability, and politicians seek to protect themselves by dumping either the policy, or the author of the policy. In this case it's too late to dump the policy. If the Labour party wants us to forget what it has done in Iraq, it must dump Blair.

You object that we tried this last year, and failed. If the biggest demonstration in British history couldn't change the way the country was run, what could? And of course it's true that we failed to stop the war with Iraq. (It may also be true that we helped to stop the wars with Iran, North Korea, Syria, Yemen, Somalia and all the other nations the idiotocracy in Washington had lined up for invasion.) But we failed partly because we appeared almost to give up after the march on February 15.

Before then, there had been lots of big talk (from me among others) of blocking motorways, disrupting ministers' speeches, occupying public buildings. But, as British people so often do, everyone waited for everyone else to act. Now we are in danger of doing the same thing. The roads and quarry protests are kicking off again, and they are timely and necessary. But if we can risk our lives to protect a landscape, we can surely take a day or two off work to bring down a government.

And it's not just because direct action works that we should try it. If Blair goes, it should be our victory, not that of the little grey men. The people must be seen to have done it. Why? Because this is about more than punishing the prime minister for what was almost certainly a war crime. It is about making sure it never happens again.

British politics is still bound by the spell of Gladstone and Churchill. Every prime minister attempts to emulate them. To be a statesman, you need a world stage on which to strut, and if you don't have one, you must borrow it from someone who does. This is why the "special relationship" persists. The establishment might break Blair, but it will not break the spell. Only the people can do that.

If we depose the prime minister through direct action, he will doubtless be succeeded by someone almost as bad, but the political context in which that someone operates will have changed. He will be forced to govern with one eye on the people, and to demonstrate that his policies differ from those of his predecessor. And the issue he would be obliged to address first is Britain's relationship with the rest of the world. Whoever succeeded Blair in these circumstances would tone down our foreign policy until it resembled that of the other northern European states.

To become a civilised, moderate, responsible nation, in other words, we must first become a nation of extremists.